So you installed a new battery and now the engine stalls? You have done nothing wrong because believe it or not this is normal. The engine computer has a learning cycle which controls the engine idle speed, when the main electrical power is interrupted which happens when you install a new battery the idle memory can be erased. When this happens the engine can either stall when idling, or idle too high, so what do you do? The answer is simple, help the computer relearn the idle speed.
Once you start the car, hold your foot slightly on the accelerator pedal enough to keep the engine running, put the car in gear and start to drive it. This will begin a new drive cycle while initiating the relearn procedure for the computer, which can take up to 30 minutes of driving. You will need to drive the car "two footed", in other words, one foot on the brake and the other on the accelerator to keep the engine from stalling out. Soon after driving for a period of time you will notice the engine being able to hold the correct idle speed on its own, this means the computer has successfully re-learned and the problem is now solved.
Yes, just the opposite problem can happen when you change the battery, the engine can idle too high, again, you have done nothing wrong, this is another computer relearn problem which a new drive cycle will solve. It can be a little uncomfortable when you put the car in-gear because the car will shake, but again once you have driven the car for a short time the computer will build a new mapping program for the engine speed and bring it down to a more acceptable range.
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